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682
FXUS64 KJAN 270350 AAB
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1050 PM CDT Sun May 26 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
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Issued at 1024 PM CDT Sun May 26 2024

As a shortwave trough swings overhead, moisture convergence has
been increasing this evening along a cold frontal boundary to our
northwest in central Arkansas. Immediately to the southeast of
this boundary, an axis of moisture and instability with MLCAPE
values are in the 3500-5000 J/kg range will support quick upscale
growth of cells developing along the front tonight. West-east
oriented deep-layer wind shear and 0-3 km shear vectors will
favor movement of any consolidating MCS to the east ahead of this
front. The corridor of best instability and moisture extending
back to the south and west will favor further development on this
western end of the front, and most high-res short-term guidance
members are now showing at least a broken line of convection
arcing back into northern Louisiana by 3-4 a.m. tonight as the
line pushes southward. Have nudged POPs some upward, but still a
little uncertain on coverage. With anticipated cold pool advancing
perpendicular to the shear vectors, damaging wind threat appears
to be isolated except if there is a bowing segment that gets
aligned more north-south along the line. Some hail is possible as
well, and a tornado cannot entirely be ruled out especially if
there is one of those bowing segments that occurs. Lastly, it does
appear we will probably get a pretty good push of the cold pool to
the south of our forecast area by morning, so dangerous heat
potential is still uncertain for tomorrow afternoon. Will evaluate
overnight if a corridor of high moisture looks to hang on in our
south through the daytime south of the front/outflow boundary.
/NF/
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&&

.DISCUSSION...
Issued at 211 PM CDT Sun May 26 2024

Through Monday:

Warm and mostly dry conditions continue this afternoon as a mid
level capping inversion keeps a lid on convective development
across most of the area. However, later tonight a cold front
currently extending from the Ozarks southward into the Red River
valley will advance eastward toward the MS River overnight as a
potent upper shortwave swings across the Midwest and TN Valley.
These features may provide the needed forcing for convection to
initiate and move into the upper ArkLaMiss Delta late this
evening. While development may initially feature a few discrete
cells, convection is expected to evolve fairly quickly into more
of a line. It is with the earlier development, especially if
things kick off a bit earlier in the evening than currently
anticipated, where storms may be more likely to take advantage of
steep mid level lapse rates and produce larger hail up to golfball
size. This is also when there is some potential for a tornado to
occur within modest low level helicity before the low level jet
begins to pull north and eastward out of the area. As storms
become more linear and cold pool dominant overnight, damaging wind
gusts will become the prevailing threat with an even more limited
brief tornado threat for any segments that can surge more
eastward within marginally supportive 0-3 km bulk shear.
Convection should lose intensity with time overnight as the cold
pool outpaces the forcing. It is worth noting that recent CAM
guidance casts some doubt over whether the forcing will be great
enough to overcome the cap, which could considerably limit
convective coverage tonight.

Forecast guidance has increasingly trended toward the cold pool from
overnight convection and/or outflows racing well south and eastward
into our area tomorrow morning, acting in effect as a cold front by
ushering in much drier air. This appears increasingly likely to
limit rain chances during the day across most of the area once any
showers clear early tomorrow morning. However, across south and east
MS and central/south LA, there is greater potential for either the
boundary to stall or retreat back into the area later in the day,
keeping greater moisture and instability around. This will result in
potential for isolated convection to redevelop Monday afternoon in
these areas. Highly conditioned on whether such redevelopment does
occur, any storms that redevelop in the afternoon could become
severe given the potential for moderate to strong instability and
marginally favorable deep shear. The window for this to occur
appears to be quite narrow, with the threat dwindling toward sunset.
Severe probabilities for the entire area during the daytime tomorrow
have been adjusted downward accordingly. /DL/

Monday night through Saturday night:

Isolated storms could linger into early Monday evening
along/south of the Highway 84 corridor, but quiet conditions are
expected for the most part.

Looking ahead from mid/late week through the weekend, while the
sensible weather over the forecast area will be slightly cooler,
less humid, and more tolerable overall, this will not be reflected
in the QPF as we will keep rain chances around just about every
day. A deep trough digging southward over the eastern CONUS will
generally keep the frontal boundary draped to our west and south,
but with the upper level pattern expected to be progressive, a mid
level ridge will build over the Plains to MS Valley region, and
this will support a relatively moist deep layer airmass over our
area. A couple of rounds of convective rainfall will possible in
the late Tue to Wed time frame as a couple of minor perturbations
move across in northwest flow aloft, but convective parameters do
not look impressive at this point and this should help keep
thunderstorm intensity below severe limits. Look for this weather
pattern to persist through late week and the weekend. /EC/

&&

.AVIATION...
(00Z TAFS)
Issued at 659 PM CDT Sun May 26 2024

VFR conditions to start the period at all TAF sites. A few
isolated SHRA or TSRA will be near KGLH, KGWO, and KGTR before
06Z, but main chance for any impacts from TSRA will be with
possible storms moving north to south through the forecast area
between the 08Z to 13Z time frame. An isolated shower or storm is
also possible in far southern Mississippi after 18Z Monday. /NF/

&&

.PRELIMINARY POINT TEMPS/POPS...
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Jackson       74  92  69  92 /  40  20  10  10
Meridian      74  93  67  93 /  60  30  10  10
Vicksburg     74  94  70  93 /  40  10  10  10
Hattiesburg   76  94  70  94 /  30  40  20  20
Natchez       74  93  70  93 /  30  20  20  20
Greenville    74  92  70  92 /  60  10  10  10
Greenwood     72  91  68  92 /  60  10  10  10
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&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&

$$

DL/EC/NF